public class Test01{
    public static void main(String[] args) {
        Circle a=new Circle();
        Circle.r=showArea(r);

    }
}
class Circle{
    double r;

    public static dobule showArea(){
        double zhouchang=0;
        zhouchang=2*3.14*r;
        return zhouchang;
    }
    public static double showPerimeter(int i){
        double mianji=3.14*r*r;
        return mianji;
    }
}